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with the most powerful means that man summon to the aid of his vision. These objects are called clusters and nebula- -clusters when near enough to permit their individual stars to be shown by the telescope, nebula when the mingled light of all their suns and systems can only be seen as a hazy cloud.

Thus have we risen in the orders of creation. We commenced with a planet and its satelites; we rose to the sun and its revolving planets, a magnificent system of orbs, all united into one great family, and governed by the same great law ; and we now find millions of these suns clustered and associated together in the formation of distinct universes, whose number, already revealed to the eye of man, is not to be counted by scores or hundreds, but has risen to thousands, while every increase of telescopic power is adding by hundreds to their catalogue.

Let us now explain these "island universes," as the Germans have aptly termed them, and attempt approximately to circumscribe their limits, and measure their distances from us, and from each other. Sir William Herschel, to whom we are indebted for this department of astronomy, conceived a plan by which it was possible approximately to sound the depths of space, and determine, within certain limits, the distance and magnitudes of the clusters and nebula within the reach of his telescopes. To convey some idea of his method of conducting these most wonderful researches, imagine a level plane, of indefinite extent, and along a straight line, separated by intervals of one mile each, let posts be placed, bearing boards on which certain words are printed in letters of the same size. The words printed on the nearest board, we will suppose, can just be read with the naked eye. To read those on the second,

telescopic aid is required, and that power which suffices to enable the letters to be distinctly seen, is exactly double that of the unaided eye. The telescope revealing the letters at the distance of three miles is threefold more powerful than the eye, and so of all the others. In this way we can provide ourselves with instruments whose space-penetrating power, compared with that of the eye, can be readily obtained.

Now to apply these principles to the sounding of the heavens. The eye, without assistance, would follow and still perceive the bright star Sirius, if removed back to twelve times its present distance. After this, as it recedes, it must be followed by the telescope. Suppose, then, a nebula is discovered with a telescope of low power, and it is required to determine its character and distance. The astronomer applies one power after another, until he finally employs a telescope of sufficient reach to reveal the separate stars of which the object is composed, which shows it to be a cluster; and since the space-penetrating power of this instrument is known, relative to that of the human eye, in case the power is one hundred times greater than that of the eye, then would the cluster be located in space one hundred times farther than the eye can reach, or twelve hundred times more remote than Sirius, or at such a distance that its light would only reach our earth after a journey of 120,000 years.

Such was Herschel's method of locating these objects in space. Some are so remote as to be far beyond the reach of the most powerful instruments, and no telescopic aid can show them other than nebulous clouds of greater or less extent. It was while pursuing these grand investigations that Herschel was led to the conclusion, that among the nebula which were visible in the heavens,

there were some composed of chaotic matter, a hazy, luminous fluid, like that occasionally thrown out from comets on their approach to the sun.

Among these chaotic masses he discovered some in which the evidences of condensation appeared manifest, while in others he found a circular disc of light, with a bright nucleus in the centre. Proceeding yet farther, he found well formed stars surrounded by a misty halo, which presented all the characteristics of what he now conceived to be nebulous fluid. Some of the unformed nebulae were of enormous extent, and among those partially condensed, such as the nebula with planetary discs, many were found so vast that their magnitude would fill the space occupied by the sun and all its planets, forming a sphere with a diameter of more than 6000 millions of miles. Uniting these and many other facts, the great astronomer was finally brought to believe, that worlds and systems of worlds might yet be in the process of formation, by the gradual condensation of this nebulous fluid, and that from this chaotic matter originally came the sun and all the fixed stars which crowd the heavens. This theory, extended, but not modified, in the hands. of Laplace, is made to account for nearly all the phenomena of the solar system, and has been already referred to in a former lecture.

For a long time, this bold and sublime speculation was looked upon, even by the wisest philosophers, with remarkable favour. The resolution of one or two nebulæ, (so classed by Herschel,) with the fifty-two feet reflector of Lord Rosse, has induced some persons to abandon the theory, and to attempt to prove its utter impossibility. All that I have to say, is, that Herschel only adopted the theory after he had resolved many hundreds of nebulæ into stars; and if there ever existed a

reason for accepting the truth of this remarkable speculation, that reason has been scarcely in any degree affected by recent discoveries.

I have examined a large number of the mysterious objects, floating on the deep ocean of space like the faintest filmy clouds of light. No power, however great, of the telescope, can accomplish the slightest change in their appearance. So distant that their light employs (in case they be clusters) hundreds of thousands of years in reaching the eye that gazes upon them, and so extensive, even when viewed from such a distance, as to fill the entire field of view of the telescope many times. Sirius, the brightest, and probably the largest of all the fixed stars, with a diameter of more than a million of miles, and a distance of only a single unit, compared with the tens of thousands which divide us from some of the nebulæ ; and yet this vast globe, at this comparatively short distance, is an inappreciable point in the field of the telescope. What, then, must be the dimensions of those objects, which, at so vast a distance, fill the entire field of view even many times repeated?

Herschel computes that the power of his great reflector would follow one of the large clusters if it were plunged so deep in space that its light would require 350,000 years to reach us, and the great telescope of Lord Rosse would pursue the same object probably to ten times this enormous distance.

Such examinations absolutely overwhelm the mind, and the wild dream of the German poet becomes a sort of dreadful sublime reality :

6

"God called up from dreams a man into the vestibule of Heaven, saying,- Come thou hither, and see the glory of my house.' And to the servants that stood around his throne he said, Take

him, and undress him from his robes of flesh : cleanse his vision, and put a new breath into his nostrils: only touch not with any change his human heart-the heart that weeps and trembles.' It was done, and with a mighty angel for his guide, the man stood ready for his infinite voyage; and from the terraces of heaven, without sound or farewell, at once they wheeled away into endless space. Sometimes with the solemn flight of angel wing they fled through Zaarrahs of darkness, through wildernesses of death, that divided the worlds of life; sometimes they swept over frontiers that were quickening under prophetic motions from God. Then, from a distance that is counted only in heaven, light dawned for a time through a sleepy film; by unutterable pace the light swept to them, they by unutterable pace to the light. În a moment the rushing of planets was upon them. In a moment the blazing of suns was around them.

“Then came eternities of twilight, that revealed, but were not revealed. On the right hand and on the left towered mighty constellations, that by self-repetitions and answers from afar, that by counter-positions, built up triumphal gates, whose architraves, whose archways,-horizontal, upright ―rested, rose—at altitude by spans that seemed ghosty from infinitude. Without measure were the architraves, past number were the archways, beyond memory the gates. Within were stairs that scaled the eternities below; above was below -below was above, to the man stripped of gravitating body depth was swallowed up in height insurmountable, height was swallowed up in depth unfathomable. Suddenly, as thus they rode from infinite to infinite, suddenly, as thus they tilted over abyssmal worlds, a mighty cry arose that systems more mysterious, that worlds more billowy,